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SGLDirect Reference
SGL Reference
DirectDraw Programming
Direct3D Programming
SGL Programming
Performance Notes
Debug and Timing Utilities
PCI Card Installation
FAQ
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Frequently Asked Questions
Contents
What do I do when I get the error
message "Cannot load SGL.DLL"?
I have an S3 868/968 graphics card and my system crashes when I
attempt to use PowerVR.
How do I set up a simple debug environment for PowerVR ?
My 2D overlay 'tears' or 'flickers' with drivers 4.0.0b4 or
later.
My SGL Direct program breaks during initialization with drivers
4.0.0b4 or later.
How do I detect which PowerVR chip (PCX1/PCX2) is present ?
Why does ConvertBMPtoSGL() not work when using a Watcom
compiler ?
What do I need to consider for bilinear mode operation ?
Does PowerVR support hardware clipping ?
Can I do n-sided polygons rather than just triangles on PowerVR
?
How do I get maximum performance with PowerVR ?
What is the most important performance optimization for PowerVR
?
Alpha Blending doesn't work in my DX5 Direct3D application.
My system locks up during sound initialisation when running
GLQuake on PCX2.
My system crashes when using PCX2 together with my Imagine 128
Series 2 graphics card.
My system hangs in VC++5.0 on exit of Direct3D application in
debugger mode.
On PCX2, frequently updated textures look corrupt - why?
Can I define Application Specific Settings (AppHints) in my
application?
My PowerVR PCX2 application crashes when playing videos. What
can I do ?
IDirectDraw4::GetDeviceIdentifier still reports PCX2 as the
active device after switching the PCX2 HAL off in the control panel. Why ?
I am using MS VisualC++5.0. Running my application in debug mode
on PCX2 makes my machine crash after the D3D device is released. What can I do ?
What do I do when I get the error message "Cannot
load SGL.DLL"?
This may be a problem with a previously run application not
closing the VXD properly.
Try running resetvxd.exe (if you have driver
version 3.1.0b4 or later). resetvxd.txt.
I have an S3 868/968 graphics card and my system crashes
when I attempt to use PowerVR.
There is a bug in some S3 chips causing an error in memory
allocation at boot time.
Have a look at the S3 memory allocation problem page to solve this
problem.
How do I set up a simple debug environment for PowerVR ?
If you are using the DirectDraw Mode of SGL Direct you can
opt to have the render not use the built-in DirectDraw surface, but blit to the GUI
screen. This can be convenient for debugging as the DirectDraw screen is not used and will
not change resolutions or create a lock on the surface.
For driver version before and including 4.0.0b3, edit
sglhw.ini and change
mode=ddraw in the [mode] section to mode=desktop.
Note that the 2D callback will not be called.
For driver version 4.0.0b4 and higher, edit sglhw.ini
and add the following
[Debug]
RenderToDesktop=1
Note that the 2D callback is called, but you may see 'tearing' due to the fact that the
GUI screen will not be locked.
My 2D overlay 'tears' or 'flickers' with drivers 4.0.0b4 or
later.
The double_buffer boolean in sgl_create_screen_device() is
observed in drivers version 4.0.0b4 or later (used to be ignored and double buffering
enabled as default).
This must now be set correctly for the desired mode - set this to TRUE if you use 2D
overlay.
My SGL Direct program breaks during initialization with
drivers 4.0.0b4 or later.
Make sure the call to sgl_use_ddraw_mode / sgl_use_address_mode()
is done before creating the SGL screen device using sgl_create_screen_device().
How do I detect which PowerVR chip (PCX1/PCX2) is present ?
In SGL / SGL Direct you can identify the
PowerVR chip by calling sgl_win_versions. This will return a pointer to a
structure containing pci_bridge_device_id, which will have one of the following values,
depending on the PowerVR chipset :
| pci_bridge_device_id |
Chipset |
| 0x001F |
Midas 3 (pre-PCX1) |
| 0x002A |
Midas 4 (PCX1) |
| 0x0046 |
Midas 5 (PCX2) |
Physically on the PowerVR board, the PowerVR chip number will reveal whether it is a PCX1
or PCX2 chip:
| PowerVR chip number |
Chipset |
| XX2010GD |
Midas 4 (PCX1) |
| XX2011GD |
Midas 5 (PCX2) |
A generic detection routine which can be used in SGL, SGL Direct and Direct3D applications
is provided together with an example windows application in the Tips and Tricks seciton.
To download this example please go to the Tips and Tricks PowerVR Detection Example section.
Why does ConvertBMPtoSGL() not work when using a
Watcom compiler ?
The current implementation of ConvertBMPtoSGL()
returns a structure compatible with Microsoft's standard. However, the returned structure
is not compatible with Watcom and therefore calls to ConvertBMPtoSGL() fail under
Watcom. A different function which will work with Watcom may be available in the future.
What do I need to consider for bilinear mode operation ?
Have a look at the SGL Direct Bilinear
Mode Considerations page.
Does PowerVR support hardware clipping under SGL Direct ?
YES. PowerVR hardware supports clipping polygons to any
rectangle of pixels without a fill rate penalty. Read the PowerVR
Fast Hardware Clipping notes to find out more.
Can I do n-sided polygons rather than just triangles on
PowerVR ?
Absolutely. Read the notes on High
Performance Polygons on PowerVR to find out how you can improve 3D performance of your
SGL Direct or Direct3D title by around 35% by using n-sided polygons.
How do I get maximum performance with PowerVR ?
Read the notes on PowerVR Performance
Optimizations.
What is the most important performance optimization for
PowerVR ?
Hardware/Software overlap. Due to the fact that PowerVR
hardware renders the 3D scene totally asynchronously from the host CPU, useful tasks can
be carried out on the CPU whilst waiting for the 3D hardware render to complete. For some
useful tips on how to do this, read the notes on PowerVR
Hardware/Software Overlap.
Alpha Blending doesn't work in my DX5 Direct3D application.
In early versions of the DirectX5 DDK (before Meltdown July
97) there was a separata flag 'ALPHABLEND' enumerated as number 42 in D3DRENDERSTATETYPE.
This flag was then merged with BLENDENABLE (27) to yield ALPHABLENDENABLE enumerated as
27. Therefore, programs compiled with an early version of DirectX5 which set the
ALPHABLEND flag will not yield any alpha blending since this flag is no longer supported
in DirectX5. The application should either be recompiled with a later version of DirectX5
and/or the ALPHABLENDENABLE flag set.
My system locks up during sound initialisation when running
GLQuake on PCX2.
We have heard of problems with PCI sound cards like the
"Monster Sound" PCI card on certain motherboard / BIOS configurations. Disabling
"PCI Streaming" in the BIOS will solve this problem and allow you to run GL
games like GLQuake and GLHexenII in optimised mode on PCX2.
My system crashes when using PCX2 together with my Imagine
128 Series 2 graphics card.
There appears to be a bug in the Imagine 128 Series 2
DirectDraw driver and/or DirectSound which eventually causes a crash if hardware page
flipping is used, eg by running PowerVR. This is a bug in the Imagine 128 drivers.
My system hangs in VC++5.0 on exit of Direct3D application
in debugger mode
This is still being investigated and we are waiting on a
report back from Microsoft. However we have a work around. There is an interaction with
the debugger itself and a call-back in our drivers (the call-back releases any data the
driver may have created). This call-back is required by Microsoft and must be called. This
works in other debuggers and only happens when the VC5 debugger is running. The work
around is to temporarily remove the calls to things like Release(pD3D) at exit. For
example, the problem routines in the DX5 SDK, e.g. ex2, are ReleaseD3D() and
ReleaseDevice(). If they are commented out and they are at the end of the game, then there
will not be a memory leakage as DDraw will clean up anyway (in fact DDraw will call the
same call-back (weird huh?) but quit OK, even in the VC debugger). Our recommendation is
to use #if DEBUG around these problem calls until we have the answer/fix from Microsoft.
On PCX2, frequently updated textures look corrupt - why?
Uploading textures to the PowerVR PCX2 card can coincide with
the card actually rendering the previous frame. This is not a problem unless you are
actually overwriting the texture which the card is rendering from at the same moment in
time. This will result in that texture appearing corrupted on the screen. In order to
solve this problem, upload the textures just before Endscene. When using Direct3D, to
ensure that PowerVR has finished rendering the previous frame, lock the render surface
using the DDLOCK_WAIT flag and then immediately unlock it again, followed by the texture
upload. In SGL Direct, use sgltri_isrendercomplete() to make sure the hardware has
finished rendering before uploading the textures.
Uploading textures just before Endscene is recommended for performance reasons also on
PCX1.
Can I define Application Specific Settings (AppHints) in my
application ?
Yes you can. Other than modifying AppHints through the
PowerVR Control Panel (via Display Properties) your application can create AppHints by
using our PVRCreateAppHint function. Go to the PowerVR
AppHints page to learn more about this and download the associated files.
My PowerVR PCX2 application crashes when playing videos.
What can I do ?
We are aware of an 'undocumented feature' which has to do
with creating / destroying DirectDraw surfaces in sequence. Typically this may happen when
creating a DirectDraw surface for playing a video and subsequently deleting that surface
and creating a new DirectDraw surface for 3D. This may cause the system to hang, probably
due to timing issues. Creating a single DirectDraw surface for 3D graphics and using that
same surface for video playback seems to solve this problem.
IDirectDraw4::GetDeviceIdentifier still reports PCX2 as the
active device after switching the PCX2 HAL off in the control panel. Why ?
Using the 3D Control Center
utility to switch between 3D hardware devices will ensure the primary HAL is correctly
selected and reported by GetDeviceIdentifier. For PCX2 detection, using our PCX runtime detection code will always work.
I am using MS VisualC++5.0. Running my application in debug
mode on PCX2 makes my machine crash after the D3D device is released. What can I do ?
This problem has now been resolved in VisualC++ version 6.0.
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